<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="jquery-3.1.1.min.js"></script>
    <style type="text/css">
        html,body {
            padding: 0;
            margin: 0;
        }
    </style>

    <script>
        function test() {
            $(window).scroll(function() {
                console.info($(window).scrollTop());
                $("img").css("opacity",$(window).scrollTop()/100);
            });


        }

    </script>
</head>
<body onload="test()">
<img src="sign.jpg" style="width: 100%">
</body>
</html>